4 files changed, 139 insertions, 12 deletions

diff --git a/src/bin/client/main.rs b/src/bin/client/main.rs
index 9018026..3407380 100644
--- a/src/bin/client/main.rs
+++ b/src/bin/client/main.rs
@@ -5,10 +5,21 @@ mod repl;
 mod tls;
 
 use repl::ClientState;
+use zagan_bet::client::paths::{database_path, default_data_dir, parse_args, USAGE};
 
 fn main() {
-    let args: Vec<String> = std::env::args().collect();
-    let unsafe_mode = args.iter().any(|arg| arg == "--unsafe");
+    let args = match parse_args(std::env::args().skip(1)) {
+        Ok(args) => args,
+        Err(message) => {
+            eprintln!("{message}");
+            std::process::exit(2);
+        }
+    };
+
+    if args.help {
+        println!("{USAGE}");
+        return;
+    }
 
     // Every game board is drawn in place, so refuse a terminal that cannot fit
     // them before touching the network or the terminal mode.
@@ -25,19 +36,33 @@ fn main() {
         std::process::exit(1);
     }
 
-    if unsafe_mode {
+    if args.unsafe_mode {
         println!("WARNING: Running in UNSAFE mode - certificate verification disabled!");
     }
 
-    connection::set_unsafe_mode(unsafe_mode);
+    connection::set_unsafe_mode(args.unsafe_mode);
 
-    let mut state = ClientState::new();
+    let data_dir = args.data_dir.unwrap_or_else(default_data_dir);
+    if let Err(error) = std::fs::create_dir_all(&data_dir) {
+        eprintln!("Cannot create {}: {error}", data_dir.display());
+        std::process::exit(1);
+    }
+    let db_path = database_path(&data_dir);
+
+    let mut state = match ClientState::new(&db_path) {
+        Ok(state) => state,
+        Err(error) => {
+            eprintln!("{error}");
+            std::process::exit(1);
+        }
+    };
     if let Some(host) = state.addr.clone() {
         state.connect_to(&host);
     }
 
     println!("Welcome to Zagan-Bet Client!");
     println!("Type 'help' for available commands.");
+    println!("Data: {}", db_path.display());
 
     state.run();
 }
diff --git a/src/bin/client/repl.rs b/src/bin/client/repl.rs
index bf02c8d..1debff1 100644
--- a/src/bin/client/repl.rs
+++ b/src/bin/client/repl.rs
@@ -43,11 +43,9 @@ pub struct ClientState {
 }
 
 impl ClientState {
-    pub fn new() -> Self {
-        let conn = rusqlite::Connection::open(
-            std::env::var("CLIENT_DB").unwrap_or_else(|_| "client.db".to_string()),
-        )
-        .unwrap();
+    pub fn new(db_path: &std::path::Path) -> Result<Self, String> {
+        let conn = rusqlite::Connection::open(db_path)
+            .map_err(|error| format!("cannot open {}: {error}", db_path.display()))?;
         database::init_db(&conn);
         let default_ip = "127.0.0.1".to_string();
         let default_port = 11525;
@@ -55,7 +53,7 @@ impl ClientState {
         let default_host = format!("{}:{}", default_ip, default_port);
         let addr = last_host.or(Some(default_host));
 
-        Self {
+        Ok(Self {
             stream: None,
             conn,
             addr,
@@ -66,7 +64,7 @@ impl ClientState {
             prompt_text: String::new(),
             terminal_size: crossterm::terminal::size().unwrap_or((MIN_COLUMNS, MIN_ROWS)),
             size_warned: None,
-        }
+        })
     }
 
     pub fn connect_to(&mut self, addr: &str) {
diff --git a/src/client/mod.rs b/src/client/mod.rs
index dc8423b..6841be3 100644
--- a/src/client/mod.rs
+++ b/src/client/mod.rs
@@ -1,4 +1,5 @@
 pub mod core;
 pub mod database;
 pub mod games;
+pub mod paths;
 pub mod ui;
diff --git a/src/client/paths.rs b/src/client/paths.rs
new file mode 100644
index 0000000..b6b8d1f
--- /dev/null
+++ b/src/client/paths.rs
@@ -0,0 +1,103 @@
+//! Client data location and command-line arguments.
+
+use std::ffi::OsStr;
+use std::path::{Path, PathBuf};
+
+pub const APP_DIR: &str = "zagan-bet";
+pub const DATABASE_FILE: &str = "client.db";
+
+pub const USAGE: &str = "\
+usage: client [-d <dir>] [--unsafe]
+
+  -d, --data-dir <dir>   where to keep client.db (default: XDG data dir)
+      --unsafe           skip certificate verification
+  -h, --help             show this message
+
+The database lives in $XDG_DATA_HOME/zagan-bet/client.db, falling back to
+~/.local/share/zagan-bet/client.db (or %APPDATA%\\zagan-bet on Windows).";
+
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct ClientArgs {
+    pub unsafe_mode: bool,
+    pub data_dir: Option<PathBuf>,
+    pub help: bool,
+}
+
+/// Parse arguments, without the program name.
+pub fn parse_args(args: impl IntoIterator<Item = String>) -> Result<ClientArgs, String> {
+    let mut parsed = ClientArgs::default();
+    let mut args = args.into_iter();
+
+    while let Some(argument) = args.next() {
+        match argument.as_str() {
+            "-d" | "--data-dir" => {
+                let Some(value) = args.next() else {
+                    return Err(format!("{argument} needs a directory\n{USAGE}"));
+                };
+                if value.is_empty() {
+                    return Err(format!("{argument} needs a directory\n{USAGE}"));
+                }
+                parsed.data_dir = Some(PathBuf::from(value));
+            }
+            "--unsafe" => parsed.unsafe_mode = true,
+            "-h" | "--help" => parsed.help = true,
+            _ => {
+                if let Some(value) = argument.strip_prefix("--data-dir=") {
+                    if value.is_empty() {
+                        return Err(format!("--data-dir needs a directory\n{USAGE}"));
+                    }
+                    parsed.data_dir = Some(PathBuf::from(value));
+                } else {
+                    return Err(format!("unknown argument: {argument}\n{USAGE}"));
+                }
+            }
+        }
+    }
+
+    Ok(parsed)
+}
+
+/// `$XDG_DATA_HOME/zagan-bet`, `%APPDATA%\zagan-bet`, or
+/// `$HOME/.local/share/zagan-bet`, in that order.
+pub fn data_dir_from(
+    xdg_data_home: Option<&OsStr>,
+    home: Option<&OsStr>,
+    appdata: Option<&OsStr>,
+) -> PathBuf {
+    if let Some(xdg) = xdg_data_home {
+        let path = Path::new(xdg);
+        // The XDG spec says a relative XDG_DATA_HOME is invalid.
+        if !xdg.is_empty() && path.is_absolute() {
+            return path.join(APP_DIR);
+        }
+    }
+
+    if let Some(appdata) = appdata {
+        let path = Path::new(appdata);
+        if !appdata.is_empty() && path.is_absolute() {
+            return path.join(APP_DIR);
+        }
+    }
+
+    if let Some(home) = home {
+        let path = Path::new(home);
+        if !home.is_empty() && path.is_absolute() {
+            return path.join(".local").join("share").join(APP_DIR);
+        }
+    }
+
+    // No usable home directory: keep the old behaviour and stay local.
+    PathBuf::from(APP_DIR)
+}
+
+pub fn default_data_dir() -> PathBuf {
+    data_dir_from(
+        std::env::var_os("XDG_DATA_HOME").as_deref(),
+        std::env::var_os("HOME").as_deref(),
+        std::env::var_os("APPDATA").as_deref(),
+    )
+}
+
+pub fn database_path(data_dir: &Path) -> PathBuf {
+    data_dir.join(DATABASE_FILE)
+}